The present invention refers to an improved type of operational process for an automatic dishwashing machine.
Automatic dishwashing machines are commonly known to be provided with a program sequence control arrangement, either of an electromechanical or an electronic type. The control adapted to control the main operating components of the machine so as to enable pre-determined operational processes of the machine to be performed in a way that has been set in advance by a user. In particular, such operational processes usually consist of one or several successive steps that can be selectively included in or excluded from a given process. A traditional operational process would basically include a main washing phase, at least one rinse phase, and a final drying phase.
Each one of these washing and rinsing phases is usually known to be performed by first letting water from the delivery mains into a washing tank. The water is appropriately enriched through the addition of detergent or rinse aid, as the case may be. The water can then be heated up to a suitable pre-established temperature, sprayed onto the washload by means of rotating spray arms that are supplied by a circulation pump, and eventually let out of the machine tank into a drain.
In general, said aforementioned amount of water filled into the machine tank is substantially the same for all of the phases included in the operational process. The amount of water is adequately large so as to ensure a correct priming of the circulation pump and also to enable each single item in the washload to be properly sprinkled and wetted. Said washload is appropriately arranged in support baskets placed one above another inside the tank of the machine.
In view of reducing the overall water usage and, as a consequence, the overall energy consumption, a proposal has been set forth in the Italian patent application no. PN91 A 000071, filed on Oct. 22, 1991, to spray the water onto the washload during the rinsing phase, at a reduced pressure with respect to the pressure used during the washing phase. This, in an advantageous manner, enables a reduced amount of water to be used during the rinsing phase, thereby bringing about a corresponding energy saving effect.
On the other hand, it is not possible to achieve such an advantageous energy saving effect during the washing phase, though it would be quite desirable.
A quite drastic reduction in the usage of energy can be obtained in a dishwashing machine of the type described in EP 0 237 994, in which the rotating spray arms are supplied in an alternate manner by the circulation pump. Such a solution, however, calls for the additional use of water-flow diverting means, which therefore makes the construction of the washing machine undesirably more complicated. U.S. Pat. No. 3 664 159 discloses even a clothes washing machine that includes spray nozzles that are supplied intermittently with water by a circulation pump. Such a solution enables the effectiveness of the washing action on the clothes to be actually boosted. However, it does not specifically bring about any reduction in the energy or, particularly, water consumption of the machine.